A rare earth metal oxide and TiO2 composite photocatalyst containing a solid superacid, its preparation method and application

Abstract

This invention discloses a rare earth metal oxide and TiO2 composite photocatalyst containing a solid superacid, its preparation method, and its application, which combines SO4 2‑ When rare earth metal oxides and TiO2 composite photocatalysts are introduced, SO4 appears in the infrared spectrum. 2‑ The characteristic vibration peaks are qualitative, and SO4 is present on the structural surface. 2‑ Solid superacid. This invention utilizes rare earth oxide composites with TiO2, where the band gap energy difference between the two semiconductor oxides enhances sunlight capture and photo-activation capabilities. A solid superacid (SO42-) is introduced into the composite photocatalytic system. 2‑ The SO42-containing catalyst is bonded to the catalyst surface in a specific manner, inhibiting photogenerated charge recombination. This invention can be used to... 2‑ The Gd2O3-TiO2 photocatalyst acts on the structure of the chromophores of dyes to remove the color from dye wastewater, thus solving the problem of difficult color removal from dye wastewater and difficulty in meeting emission requirements.

Description

Technical Field

[0001] The present invention relates to the field of photocatalysis technology, and in particular to a rare earth metal oxide containing solid superacid and TiO2 composite photocatalyst, a preparation method therefor and use thereof. Background Art

[0002] Rare earth elements have some special electronic structures and catalytic properties, so researches on compounding rare earth oxides with TiO2 have aroused wide interest. Rare earth elements are not rare. Among the 14 elements after lanthanides, that is, from cerium to lutetium, there are 7 inner 4f orbitals, each of which can accommodate two electrons with opposite spin directions, so the ideal arrangement of their electrons is 4f 1+n 5d 1 6s 2 (n=0 to 13). However, since the energy level of 4f orbitals is lower than that of 5d orbitals, electrons are often filled in the inner 4f orbitals. According to actually measured results, 5d orbitals are empty, which provide electron transfer orbitals for other electrons and become "electron transfer stations for catalysis". This is the reason why rare earth elements and their compounds have high catalytic activity.

[0003] At present, the application of rare earth element oxides compounded with TiO2 to degrade environmental pollutants has become a research hotspot. For example, both La2O3 / TiO2 and Y2O3 / TiO2 composite photocatalysts follow the rule that their photocatalytic activity is superior to that of single TiO2. Although the photocatalyst compounded by TiO2 and rare earth metal oxide has good photocatalytic activity, its activity under visible light conditions is unsatisfactory.

[0004] Solid superacid refers to solid acid that is stronger than 100% sulfuric acid. In terms of Hammett acidity function, it refers to solid acid with -16.04<H0<-11.92 (H0 of 100% sulfuric acid = -11.93). The acidity of solid superacid can be more than 10,000 times that of 100% sulfuric acid. Superacid composed of sulfate and oxides (-16.04<H0<-14.52) has attracted much attention recently. SO4 2- / M x O y type solid superacid has very high activity for many acid-catalyzed reactions, and research and application of solid superacid have become a hotspot field for searching for novel green and environmentally friendly catalysts.

[0005] Chinese patent application No. 201811026084.0 discloses a rare earth element modified titanium dioxide nanophotocatalyst material for photocatalytic degradation of VOCs and its preparation method; Chinese patent application No. 201110290463.2 discloses a method for preparing sulfur-doped titanium dioxide visible light catalyst. However, the prior art does not disclose rare earth metal oxide and TiO2 composite photocatalyst containing solid superacids, its preparation method and application. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a composite photocatalyst containing a solid superacid, rare earth metal oxide, and TiO2, along with its preparation method and applications. This solves the problem of low catalytic activity of existing TiO2 and rare earth metal oxide composite photocatalysts under visible light conditions.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0008] Firstly, a rare earth metal oxide and TiO2 composite photocatalyst containing a solid superacid is provided to convert SO42- into a more reactive form. 2- When rare earth metal oxides and TiO2 composite photocatalysts are introduced, SO4 appears in the infrared spectrum. 2- The characteristic vibration peaks are qualitative, and SO4 is present on the structural surface. 2- Solid superacid.

[0009] Furthermore, the rare earth metal oxide is Gd2O3, and the XRD pattern shows characteristic cubic Gd2O3 diffraction peaks and anatase TiO2 diffraction peaks.

[0010] Secondly, a method for preparing a rare earth metal oxide and TiO2 composite photocatalyst containing a solid superacid is provided, specifically including the following steps:

[0011] Step 1-1: Add 10 mL of 2.89 mol / L titanium sulfate solution dropwise to 26 mL of anhydrous ethanol while stirring vigorously to obtain solution A;

[0012] Steps 1-2: Dissolve 0.5234g of Gd2O3 in 30mL of 1mol / L sulfuric acid and mix with 6mL of anhydrous ethanol to prepare solution B;

[0013] Steps 1-3: Add solution B dropwise into solution A under vigorous stirring to obtain SO4. 2- / Gd2O3-TiO2 sol, the obtained sol was dried in an oven and then ground into powder;

[0014] Step 4: Calcine the powder at 300℃ for 2 hours to obtain SO4. 2- / Gd2O3-TiO2 photocatalyst.

[0015] Thirdly, this invention provides an application of a composite photocatalyst of gadolinium oxide and TiO2, which is a solid superacid, in removing color from dye wastewater.

[0016] The beneficial effects of this invention are as follows:

[0017] (1) By utilizing rare earth oxides to composite TiO2, the band gap energy difference between the two semiconductor oxides is used to improve the ability to capture sunlight and activate it through photoexcitation. A solid superacid (SO4) is introduced into the composite photocatalytic system. 2- They are bonded to the catalyst surface in a certain form to suppress photogenerated charge recombination.

[0018] (2) The SO4 of the present invention can be used 2- / Gd2O3-TiO2 photocatalyst acts on the structure of the chromophores of dyes to remove the color from dye wastewater, thus solving the problem of difficult color removal from dye wastewater and difficulty in meeting emission requirements. Attached Figure Description

[0019] Figure 1 SO4 2- Infrared spectrum of Gd2O3-TiO2 photocatalyst;

[0020] Figure 2 SO4 2- XRD pattern of Gd2O3-TiO2 photocatalyst;

[0021] Figure 3 SO4 2- Electron microscopy and energy dispersive spectroscopy (EDS) images of Gd2O3-TiO2 photocatalyst;

[0022] Figure 4 To avoid adding SO4 2- Infrared spectrum of Gd2O3-TiO2 photocatalyst;

[0023] Figure 5 To avoid adding SO4 2- XRD pattern of Gd2O3-TiO2 photocatalyst;

[0024] Figure 6 To avoid adding SO4 2- Electron microscopy and energy dispersive spectroscopy (EDS) images of Gd2O3-TiO2 photocatalysts. Detailed Implementation

[0025] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0026] Example 1

[0027] 10 mL of a titanium sulfate solution of a certain concentration was added dropwise to 26 mL of anhydrous ethanol under vigorous stirring to obtain solution A. 0.2617 g of Gd₂O₃ was dissolved in 20 mL of 1 mol / L sulfuric acid and mixed with 16 mL of anhydrous ethanol to prepare solution B. Solution B was then added dropwise to solution A under vigorous stirring to obtain SO₄²⁻. 2- Gd₂O₃-TiO₂ sol was dried in an oven and then ground into powder; the powder was then calcined at 300℃ for 2 hours to obtain SO₄²⁻. 2- / Gd2O3-TiO2 photocatalyst.

[0028] Example 2

[0029] 10 mL of a titanium sulfate solution of a certain concentration was added dropwise to 26 mL of anhydrous ethanol under vigorous stirring to obtain solution A. 0.5234 g of Gd₂O₃ was dissolved in 36 mL of 1 mol / L sulfuric acid and mixed with 16 mL of anhydrous ethanol to prepare solution B. Solution B was then added dropwise to solution A under vigorous stirring to obtain SO₄²⁻. 2- Gd₂O₃-TiO₂ sol was dried in an oven and then ground into powder; the powder was then calcined at 300℃ for 2 hours to obtain SO₄²⁻. 2- / Gd2O3-TiO2 photocatalyst.

[0030] Example 3

[0031] 10 mL of a titanium sulfate solution of a certain concentration was added dropwise to 26 mL of anhydrous ethanol under vigorous stirring to obtain solution A. 1.0469 g of Gd₂O₃ was dissolved in 46 mL of 1 mol / L sulfuric acid and mixed with 16 mL of anhydrous ethanol to prepare solution B. Solution B was then added dropwise to solution A under vigorous stirring to obtain SO₄²⁻. 2- Gd₂O₃-TiO₂ sol was dried in an oven and then ground into powder; the powder was then calcined at 300℃ for 2 hours to obtain SO₄²⁻. 2- / Gd2O3-TiO2 photocatalyst.

[0032] Comparative Example 1

[0033] 10 mL of tetrabutyl titanate was added dropwise to 26 mL of anhydrous ethanol under vigorous stirring to obtain a pale yellow transparent solution A. 0.5234 g of Gd₂O₃ was dissolved in 36 mL of 1 mol / L sulfuric acid and mixed with 16 mL of anhydrous ethanol to prepare solution B. Solution B was added dropwise to solution A under vigorous stirring to obtain a sol. The sol was dried, ground into powder, and calcined at 300 °C for 2 hours to obtain an SO₄²⁻-free solution. 2- Gd2O3-TiO2 photocatalyst.

[0034] like Figure 1 As shown in the infrared spectrum, 3400 and 1633 cm⁻¹ -1 The peak at that location should be attributed to a metal oxide (M). x O y The presence of surface hydroxyl groups and adsorbed OH groups in water enhances the photocatalytic activity of the gas phase. Hydroxyl radicals are important oxidants in gas-phase reactions, and the presence of solid superacids is beneficial to the presence of surface hydroxyl groups. This can improve the gas-phase photocatalytic activity by inhibiting the recombination of photogenerated electrons and holes and by promoting the growth of hydroxyl radicals. (1100cm) -1 The absorption peak can be attributed to an inorganic chelate double-coordinate bond containing ionic S=O bonds, 987 cm⁻¹. -1 The absorption peak at that point is due to covalent sulfate adsorption. Therefore, SO42- 2- SO4 is complexed on the Gd2O3-TiO2 surface in a chelate dual-coordination manner. 2- After the displacement, due to SO4 2- The inductive effect of SO42- can increase the acidity of other hydroxyl groups, giving it the function of a β-acid. Meanwhile, SO42-... 2- Coordination adsorption on the TiO2 surface shifts the electron cloud intensity of the Ti-O bond, thus affecting the Ti... 4+ It has stronger L-acidity.

[0035] like Figure 2 As shown, the characteristic diffraction peaks in the spectrum correspond to the 101, 004, 200, 105, and 204 crystal planes of anatase TiO2. Simultaneously, the characteristic diffraction peaks in the XRD pattern correspond to the 222, 400, 440, and 622 crystal planes of cubic Gd2O3. This indicates that the photocatalyst is mainly composed of TiO2 and Eu2O3. The study shows that the incorporation of Gd causes lattice expansion in TiO2, leading to increased lattice distortion and inhibiting the phase transformation and particle size growth of TiO2. The Gd2O3-TiO2 sample is composed of anatase TiO2 and cubic Gd2O3.

[0036] like Figure 3As shown, the horizontal axis of the spectrum represents the characteristic X-ray peaks of the elements, in kV, which is also the pulse height and is related to the element type; the vertical axis represents the pulse number, in CP, which is the number of X-ray photons collected, and the peak height is related to the element content being analyzed. Thus, the qualitative analysis yielded the following element types in the sample: O, S, Ti, and Gd, which are consistent with the XRD analysis results.

[0037] Photocatalysis test results:

[0038] Under acidic conditions (pH 3), with an initial concentration of methylene blue of 10 mg / L, after 30 minutes of light irradiation, the photocatalyst SO4... 2- The bleaching rate of Gd2O3-TiO2 (Ti:Gd = 1:0.05) for methylene blue was 85%; while under the same conditions, the bleaching rate of the photocatalyst Gd2O3-TiO2 (Ti:Gd = 1:0.05) without solid acid was 60%.

[0039] This invention utilizes rare earth oxides to composite TiO2, where the band gap energy difference between the two semiconductor oxides enhances sunlight capture and photo-activation capabilities. A solid superacid (SO42-) is introduced into the composite photocatalytic system. 2- The SO42-containing catalyst is bonded to the catalyst surface in a specific manner, inhibiting photogenerated charge recombination. This invention can be used to generate SO42-. 2- / Gd2O3-TiO2 photocatalyst acts on the structure of the chromophores of dyes to remove the color from dye wastewater, thus solving the problem of difficult color removal from dye wastewater and difficulty in meeting emission requirements.

[0040] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0041] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A rare earth metal oxide and TiO2 composite photocatalyst containing a solid superacid, characterized in that, SO4 2- When rare earth metal oxides and TiO2 composite photocatalysts are introduced, SO4 appears in the infrared spectrum. 2- The characteristic vibration peaks are qualitative, and SO4 is present on the structural surface. 2- Solid superacid; the rare earth metal oxide is Gd2O3, and the XRD pattern shows characteristic cubic Gd2O3 diffraction peaks and anatase TiO2 diffraction peaks; The preparation method of the rare earth metal oxide and TiO2 composite photocatalyst containing solid superacid specifically includes the following steps: Step 1-1: Add 10 mL of 2.89 mol / L titanium sulfate solution dropwise to 26 mL of anhydrous ethanol while stirring vigorously to obtain solution A; Steps 1-2: Dissolve 0.5234g of Gd2O3 in 30mL of 1mol / L sulfuric acid and mix with 6mL of anhydrous ethanol to prepare solution B; Steps 1-3: Add solution B dropwise into solution A under vigorous stirring to obtain SO4. 2- / Gd2O3-TiO2 sol, the obtained sol was dried in an oven and then ground into powder; Step 4: Calcine the powder at 300℃ for 2 hours to obtain SO4. 2- / Gd2O3-TiO2 photocatalyst.

2. The application of the rare earth metal oxide and TiO2 composite photocatalyst containing solid superacid as described in claim 1 in removing color from dye wastewater.

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